The present embodiments relate to a high-voltage measurement divider.
In X-ray installations, X-ray tubes that require, for example, over 150 kV for generating X-ray radiation are increasingly used. Such X-ray tubes are not divided in ground-symmetrical fashion between the cathode and the anode. Instead, X-ray tubes that are operated in single-pole fashion (e.g., the anode is at the ground potential) are being used increasingly often.
For example, X-ray tubes that are used for computed tomography have a rotary anode in order to be able to distribute the heat produced from the high absorbed electron energy more effectively over the anode during operation. Single-pole operation of the X-ray tube has the advantage, inter alia, that involved insulation of the motor of the rotary anode, with respect to the surrounding environment at ground potential, may be dispensed with.
Single-pole operation of an X-ray tube places more stringent requirements on the dielectric strength of the voltage measurement, however, due to the higher potential difference with respect to ground. In order to measure the voltage across an X-ray tube, a high-voltage measurement divider that divides a high voltage present at two ends of the X-ray tube into individual division stages, in accordance with a known ratio, may be used. Therefore, a conclusion may be drawn with respect to the total voltage drop between the two ends from the voltage measured at the ends of a division stage.
While a resistive voltage division is used to measure the DC voltage component, the division stages of a high-voltage measurement divider may also have a capacitive voltage division in order to be able to precisely detect radiofrequency components of the voltage (e.g., in the case of switch-on operations or else voltage fluctuations (ripple)).
In the case of the capacitive components, however, a sufficient dielectric strength is to be provided. While a dielectric strength of the high-voltage measurement divider of 100 kV is in most cases sufficient during ground-symmetrical operation with tolerances, the high-voltage measurement divider is to be designed for an applied voltage that is twice as high in the case of a single-pole X-ray tube. Since, however, there is often only a limited amount of physical space available in an X-ray installation, a high-voltage measurement divider may not be enlarged as desired. For example, the addition of capacitors that may withstand high voltages may not be possible for reasons of space.